The present invention relates generally to an electrical jack for use in conjunction with a pin-plug, and more particularly to a resilient contact member which engages resiliently with a pin portion of the pin-plug inserted into the jack.
There have been proposed various kinds of jacks. FIG. 1 is a cross section showing an embodiment of one known jack. A jack 1 comprises a resilient contact member 2 which is secured to an inner wall of a housing 3. The contact member 2 is formed by bending a metal strip of a relatively large width into a substantially U-shaped form. The contact member 2 comprises a fixed leg portion 8 and a movable leg portion 10 connected to the leg portion 8 by means of a U-shaped bent portion 6. When a pin-plug 4 is inserted into the jack 1, the movable leg portion 10 is displaced from a position illustrated in FIG. 1 by a chain line due to an engagement of the movable leg portion 10 with a pin portion 5 of the plug 4. Each time the pin-plug 4 is inserted into and pulled out of the jack 1 the bent portion 6 of the contact member 2 is deformed and thus is fatigued. Therefore the resiliency or elasticity of the contact member 2 becomes gradually decreased. In an extreme case the bent portion 6 might be deformed beyound its elastic limit and could not return to its original position. In this manner a contact pressure of the contact member 2 with respect to the pin portion 5 becomes small and thus an electrical property of the pin-plug and jack connection is deteriorated to a great extent.
In order to avoid the above mentioned drawback of the known jack shown in FIG. 1 there have been devised several other jacks. FIG. 2a shows an embodiment of such a jack. In this jack 1 a projection 7 is formed on the inner wall of a housing 3 and a fixed leg portion 8 of contact member 2 is provided with a hole 9 as illustrated in FIG. 2b. As shown in FIG. 2a the contact member 2 is secured to the housing 3, while the projection 7 is inserted into the hole 9. The projection 7 has such a length that it can limit the displacement of the movable leg portion 10 of the contact member 2.
FIGS. 3a, 3b and 3c show other embodiments of the known contact member 2 of FIG. 2b. In the contact member of FIG. 3a between a fixed leg portion 8 and a movable leg portion 10 is inserted a coiled spring 11. In the embodiment illustrated in FIG. 3b a resilient lead like strip 12 is formed integrally with a fixed leg portion 8 and a free end of the strip is urged against a movable leg portion 10. In a contact member 2 shown in FIG. 3c a projection 13 made of insulating material is secured to a fixed leg portion 8.
The contact members illustrated in FIGS. 2 and 3 can overcome the disadvantage of the contact member shown in FIG. 1 and the movable leg portion 10 can be effectively prevented from being deformed beyond its elastic limit. However it is rather difficult to manufacture such contact members. It is apparent that the manufacture of such contact members requires at least one additional step. Particularly in case of a jack of small size the contact member could not be formed from a relatively wide metal strip, but has to be made of a thin metal strip such as a metal wire. In this case the above mentioned reinforcing means could not be applied at all.